Electrical currents can cause damage in bearings. It is known that currents of the order of microamperes to amperes result in decarburization and sparking.
From the prior art oil filters are available, which are intended to prevent the lubricant to be filtered from becoming electrically charged. Such a filter is described, for example, in the document DE 10 2010 025 215 A1.
Recent research has shown that even small currents in the range of a few microamperes can be critical. It is suspected that such currents give rise to so-termed White Etching Cracks (WEC). However, the solutions known from the prior art are not suitable for eliminating currents in the microampere range.